1. Technical Field
The present invention relates to a variable duct apparatus for a vehicle disposed at the front of the vehicle to adjust the amount of air to be introduced into the front of the vehicle.
2. Related Art
In general, the bumper and/or the front grille which are disposed at the front of a vehicle have an open air grille for introducing air into the front face of a radiator disposed at the front of the vehicle. The air introduced through the air grille cools coolant in the radiator.
During high speed running, running resistance increases as the amount of air introduced into the front of the vehicle through the open air grille of the bumper and/or the front grille increases, whereby fuel efficiency may be reduced. The engine may be excessively cooled in the winter or in a cold region or during continuous high speed running. In addition, the warm-up performance of the engine and the catalytic activity of an exhaust gas purifier device may be affected in the winter or in a cold region.
As a solution to these concerns, a variable duct apparatus has been proposed which is disposed between the bumper and the radiator to adjust the amount of air introduced into the front of the vehicle according to a vehicle speed and a temperature change of the engine coolant.
As an example of a variable duct apparatus, in Japanese Unexamined Patent Application Publication (JP-A) No. 2010-247819 discloses a shutter device. The shutter device in JP-A No. 2010-247819 includes multiple movable fins and an electric motor. The multiple movable fins are arranged at intervals in the vertical direction in an air flow passage formed of a case frame. The electric motor integrally rotates the movable fins around respective axes. The movable fins has a defined operational range which is between an open position and a closed position, the open position allowing air to be introduced into the front of the vehicle, the closed position causing the introduction of air to be blocked or reduced. From a side of the case frame, a prevention unit projects which prevents an operation that causes all the movable fins to exceed the defined operational range, by contact of a single movable fin.
The electric motor is energized for a predetermined time so as to rotate the movable fins from the open position to the closed position or from the closed position to the open position.
An operating time, which is from the start of energization of the electric motor until a lock current value is detected, is measured, the lock current being caused by prevention of a rotational operation of the movable fins, and an abnormal operation of the movable fins is determined based on whether or not the measured operating time is out of the reference time range.
For another example, JP-A No. 2012-25175 disclose a variable shutter device that includes multiple shutters and a slide link. The shutters are fixed to a shutter base and have plate vanes rotatably attached to multiple shafts. The slide link connects the plate vanes. The shutter base is provided with upper and lower stoppers which control the movement of the slide link at an open position and a closed position, respectively. In addition, a return spring is disposed between the upper part of the slide link and the shutter base in a stretched manner so as to urge the plate vanes in a blocking direction. The slide link is connected to an arm link which is rotated by the electric motor.
When power supply to the electric motor is stopped, the slide link is urged toward the open position by the return spring, so that the plate vanes are held in the open position, the open position causing the slide link to come into contact with the upper stopper. On the other hand, when the electric motor is rotated by power supply thereto, the slide link is moved to the closed position against the return spring by the arm link which rotates integrally with the electric motor, so that the plate vanes are rotated up to the closed position, the closed position causing the slide link to come into contact with the lower stopper.
A failure of the shutter is detected by detecting an induced voltage of the electric motor when the slide link is moved from the closed position to the open position by the return spring after power supply to the electric motor is stopped.
According to JP-A No. 2010-247819, abnormality of the movable fins is detected based on whether or not the operating time from the start of energization of the electric motor until detection of a lock current value is within a reference time range. The operating time is detected by contact of the prevention unit with one of the multiple interlocking movable fins. Thus, even if a movable fin other than the movable fin in contact with the prevention unit falls off, or a unit for interlocking the movable fins has a failure, the operation is normal may be erroneously determined to be normal. In addition, since the prevention unit, which projects from the case frame, receives a heavy load due to contact with the movable fins at the open position, rigidity for preventing deformation of the case frame is necessary, and thus the shape of the case frame is limited.
In JP-A No. 2012-25175, the plate vanes rotatably attached to the multiple shafts are connected to the slide link, and a failure of the shutter is detected by detecting an induced voltage of the electric motor which is caused by a movement of the slide link. Thus, even if an operation of the plate vanes has a failure, for example, a plate vane falls off, or a joint connecting the slide link and the plate vanes falls off, erroneous determination indicating that the operation may erroneously be determined to be normal.